JPH06293118A - Soft multilayered film - Google Patents

Abstract

PURPOSE:To provide a packing material not impairing the flexiblity and close adhesion of a film and being excellent in pinhole resistance and oxygen barrier properties. CONSTITUTION:A soft multilayered film contains at least a nylon layer (A), a gas barrier layer (B), an adhesive layer (C) and an ethylene/vinyl acetate copolymer layer (D) with vinyl acetate content of 10% or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible and contents-containing material used in a vacuum packaging form (hereinafter referred to as a skin pack) in which a film is heated on a hot platen and then the film is brought into close contact with the contents by air pressure while being heat-sealed. The present invention relates to a soft multilayer film for food packaging that has excellent adhesion to.

[0002]

2. Description of the Related Art Deep-vacuum vacuum packaging is generally used for packaging processed animal products and processed marine products, and usually a film having an oxygen gas barrier property is used to enhance the preservation of the contents. An ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) or a vinylidene chloride resin (hereinafter referred to as PVDC) is used for the oxygen gas barrier layer. Deep-draw vacuum packaging is suitable for those with a relatively smooth surface and uniform shape, but if the contents are not uniform in shape and surface or sliced ones are arranged side by side, a film Since the molding size is larger than the contents, the film formed during vacuum packaging remains as wrinkles on the surface of the package and remains unattractive, and pinholes easily occur in the wrinkles. It causes trouble. In addition, if the adhesion is poor after packaging, drip is accumulated between the film and the contents to deteriorate the appearance, and further deteriorate the quality. Therefore, irregularly shaped or sliced items arranged in a line are skin-packed, but it is preferred that the film used is flexible and easy to stretch, and because it is compatible with the packaging method, conventionally it is mainly soft chloride. A film having a constitution of vinyl (hereinafter referred to as PVC) / PVDC / ethylene-vinyl acetate copolymer (hereinafter referred to as EVA) is used. However, products related to processed livestock products and processed fishery products are generally distributed at a low temperature of 10 ° C. or lower, and in the above-mentioned multilayer film, pinholes may be generated in the distribution process, which may impair the storability of the contents. More recently, due to environmental issues, resins containing halogen (PVC, PVDC
Etc.) is not being used as a packaging material, and it is spreading rapidly from downstream. Under such circumstances, the flexible film was studied, but initially, considering the softening, the so-called hard resin other than EVOH of the oxygen gas barrier layer was examined in the direction of removing it from the layer structure. However, the packaging machine widely used by users for skin packs has a different mold structure of the vacuum chamber section from the general packaging machine, so a part of the film is heated strongly at the initial stage, and the film is heated closely to the heating plate in vacuum. When heated, only the part that was heated strongly was stretched and a perforation phenomenon was observed.

[0003]

DISCLOSURE OF THE INVENTION The present invention does not impair the flexibility and adhesiveness of the film and allows the user to use the conventional packaging machine as it is and has a pinhole resistance.
It is to provide a packaging material having an excellent oxygen gas barrier property.

[0004]

The present invention provides a nylon layer (A), a gas barrier layer (B), an adhesive layer (C) and an ethylene-vinyl acetate copolymer layer (D) having a vinyl acetate content of 10% or more. ) Is a flexible multilayer film containing at least the layer of.

The nylon layer (A) used in the present invention is 6
Nylon, 6-6 nylon, 6-10 nylon, 6-1
2 nylon, 11 nylon, 12 nylon, copolymers thereof, amorphous nylon, MXD6 nylon obtained by polycondensation of metaxylylenediamine and adipic acid, and blends thereof are used. Considering the adhesiveness of the skin pack, 6 nylon, 6.6
6 nylon and 6/12 nylon are preferred. Nylon has excellent heat resistance, cold resistance, and mechanical strength, so it can add mechanical strength such as pinhole resistance to packaging materials.
Incorporation on the outside of the multilayer film can impart pinhole resistance particularly to external impact. The gas barrier layer (B) is EVOH and has an ethylene content of 25 to 75 mol% and a saponification degree of 90% to vinyl acetate in the copolymer.
The above is preferable, and in consideration of flexibility, the melting point (DSC method) is 130 ° C. or lower and the Young's modulus is 20 ° C., 6
EVOH of 130 kg / mm ² or less under 5% RH
Is more preferable. The adhesive layer (C) includes polyethylene, polypropylene, copolymers thereof, copolymers with different α-olefins, ethylene-vinyl acetate copolymers and the like, and monobasic unsaturated fatty acids such as acrylic acid and methacrylic acid. Alternatively, an acid-modified olefin resin obtained by chemically binding an anhydride of a dibasic unsaturated fatty acid such as maleic acid, phthalic acid, or itaconic acid, that is, maleic anhydride is used. Furthermore, the EVA layer (D) is EVA having a vinyl acetate content of 10% or more, and the vinyl acetate content is preferably 15 to 25% from the viewpoint of flexibility and processability.

In the method for producing a flexible multilayer film of the present invention, a coextrusion method, a dry laminating method and the like are used. In the dry laminating method, the use of an adhesive causes the film to become so stiff and hard that it is flexible. Considering the above, the coextrusion method is preferable. As described above, EVOH is preferable for the gas barrier layer. When the melting point of the nylon layer is equal to or lower than that of EVOH, the mold structure of the vacuum chamber part is different from the general mold in the skin pack packaging machine currently widely used by users. A part of is strongly heated in the initial stage, and when the film is heated in close contact with a heating plate in a vacuum, only the strongly heated part is stretched to have a very thin thickness, or in some cases, a perforation phenomenon is observed. Therefore, for the nylon layer used in the present invention, it is preferable to use nylon having a melting point of 20 ° C. or more higher than that of EVOH because it is necessary to maintain the mechanical strength so that the thickness does not become thin even if a part of the film is strongly heated. But 100 ° C
If the melting point is higher than the above, the film will not be sufficiently softened even when heated by a hot platen, and the adhesiveness after packaging will be significantly reduced. Nylon layer and EVOH in terms of pinhole resistance and gas barrier properties
The layer needs to have a certain thickness, but if it is too thick, the flexibility of the film is impaired and the adhesion is lost.
Therefore, the total thickness of the nylon layer and the gas barrier layer is preferably 30% or less of the total thickness of the film.

[0007]

In the skin pack, adhesion to the contents is required, but if PVC or PVDC is not used, so-called hard resin other than EVOH, which is the gas barrier layer, is excluded from the layer structure in order to impart flexibility to the film. It was examined in the direction of doing. However, since the packaging machine widely used for skin packs has a different mold structure from that of a general packaging machine, the conventional flexible film cannot avoid the perforation phenomenon when the film is heated. In addition to EVOH, the film of the present invention uses nylon, which has a high softening temperature and mechanical strength to some extent, so that even when a part of the film is strongly heated at the initial stage in the vacuum chamber part of the skin pack packaging machine, it is sharp Since the softening did not occur and the entire film was stretched relatively, the perforation phenomenon was greatly improved. Furthermore, nylon has high mechanical strength, which allows the film thickness to be made thinner than before, leading to improved adhesion. Also, by using nylon as the outermost layer resin, it is possible to sterilize the boil and it can be widely used for food packaging.

[0008]

EXAMPLE A multilayer film having the layer structure shown in Table 1 was prepared by a coextrusion method. The thickness of all the obtained films is 80 μm
Met. The resins and symbols used are as follows.・ Ny1: 6 nylon UBE nylon 1 made by Ube Industries
030B ・ Ny2: 6-12 nylon UBE nylon 7024B made by Ube Industries Ltd. ・ EVOH1: Kuraray's Eval EP-S105 Young's modulus 120Kg / mm ²・ EVOH2: Kuraray's Eval EP-E105 Young's modulus 150Kg / mm ²・ Adhesive resin: Mitsui Petrochemical Industry Admer VF60
0 ・ EVA1: Mitsui DuPont Polychemical Evaflex P2505C ・ EVA2: Mitsui DuPont Polychemical Evaflex P1403C ・ ION1: Mitsui DuPont Polychemical made Himilan H1601 The obtained film was packed in a packing machine and packed with bacon. And the thickness were examined. For gas barrier property, the amount of oxygen permeation of the film was measured with OXTRAN of Mocon Co.
The results are shown in Table 2.

[0009]

[0010] Note Adhesion: ○ Keep the shape of the contents and adhere without gaps. △ The corners of the contents are slightly deformed and there are some gaps. × The shape of the contents is greatly deformed. Wrinkles: Almost no wrinkles are found on the package △ Some wrinkles are found on the package × Many large wrinkles are found on the package Perforation: ○ Thickness inside the seal is 25 μm or more △ Thickness inside the seal Is 15 μm or less, but there is no perforation. × Perforation is found inside the seal. Gas barrier property: Oxygen permeation amount (23 ° C × 65% RH) ○ 10 cc / m ² · D or less △ 20 cc / m ² · D or less × 20cc / m ² · D or more

[0011]

The flexible multilayer film of the present invention is excellent in oxygen gas barrier property, sealing property, flexibility and adhesiveness and has a conventional P content.
With the exception of the VC / PVDC type film, it was possible to wrap without problems even with the method that was considered difficult to wrap. Furthermore, it is a packaging material for skin packs that does not use a halogen-based resin and can adapt to recent environmental problems.

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Claims (13)

[Claims] 1. A soft material containing at least a nylon layer (A), a gas barrier layer (B), an adhesive layer (C) and an ethylene-vinyl acetate copolymer layer (D) having a vinyl acetate content of 10% or more. Multilayer film. 2. The flexible multilayer film according to claim 1, wherein the gas barrier layer (B) is an ethylene-vinyl alcohol copolymer. 3. The gas barrier layer (B) has a melting point (DSC).
The soft multilayer film according to claim 2, which is an ethylene-vinyl alcohol copolymer having a Young's modulus of 130 ° C or lower and a Young's modulus of 20 ° C and 65% RH of 130 kg / mm ² or less. 4. The nylon layer (A) comprises 6 nylon, 6 ·
6. Nylon 66 or 6.12.
Or the flexible multilayer film according to item 3. 5. The gas barrier layer (B) is an ethylene-vinyl alcohol copolymer, and the melting point (DS) of the nylon layer (A).
The soft multilayer film according to claim 1, wherein the C method) Tn satisfies the following relational expression with the melting point (DSC method) Te of the ethylene-vinyl alcohol copolymer. 20 ° C <Tn-Te <100 ° C 6. A nylon layer (A) and a gas barrier layer (B)
The total thickness of the flexible multilayer film according to claim 1, which is 30% or less of the total thickness of the film. 7. An ethylene-vinyl acetate copolymer layer (D)
The vinyl acetate content of 15% to 25%.
The soft multilayer film according to 2, 3, 4, 5 or 6. 8. The layer structure is (A)-(B)-(C)-
(D) The soft multilayer film according to claim 1, 2, 3, 4, 5, 6 or 7. 9. The layer structure is (A)-(C)-(B)-
(C)-(D), The flexible multilayer film of Claim 1, 2, 3, 4, 5, 6 or 7. 10. The layer structure is (B)-(A)-(C)-
(D) The soft multilayer film according to claim 1, 2, 3, 4, 5, 6 or 7. 11. The layer structure is (B)-(C)-(A)-
(C)-(D), The flexible multilayer film of Claim 1, 2, 3, 4, 5, 6 or 7. 12. The layer structure is (A)-(B)-(A)-
(C)-(D), The flexible multilayer film of Claim 1, 2, 3, 4, 5, 6 or 7. 13. The method according to claim 1, which is manufactured by a co-extrusion method.
2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12
The soft multilayer film described.